The invention relates to holders of the type used for the attachment and sealing of bag-like annular filter tubes which comprise a supporting basket suspended from an end plate. The supporting basket has a venturi tube at its upper end which merges upwardly and outwardly into a widened-out annular collar, the conically constructed annular face of which can be pressed against a sealing ring, the filter tube being interposed between the sealing ring and the annular face.
Threaded holders of this type are used for attaching a filter tube unit to the end plate in a container, particularly in air purifying installations, in order to cleanse the air emanating from an industrial process which is contaminated by small particles. The purpose of the threaded holder is to secure the filter tube in sealing-tight fashion to the end plate but permit easy replacement of the filter tube when it becomes torn or clogged.
A known threaded holder of the aforementioned type is disclosed in U.S. Pat. No. 3,856,489. The known holder has two conical portions which, for sealing the filter tube, have to be moved onto each other and against a threaded supporting means which is suspended from the end plate. The filter tube is clamped between these conical portions along which a continuous seal is formed. The purpose of this is to prevent unfiltered air passing into a part of the unit carrying the filtered or purified air. However, the known threaded holder also has a second seal between the top of the annular collar of the tube and a portion of the threaded supporting means to provide a double seal and to prevent unfiltered air leaking into the filter unit. For example, it may happen that the first-mentioned seal with the two conical portions becomes defective due to irregularities, whereupon this secondary seal is intended to take over the sealing function.
A disadvantage of the known threaded holder is that the filter tube, the supporting basket and also the screwed holder must be detached from the side on which the dust-laden gas or air is present, i.e. from the underside of the end plate. It can happen that parts of the known attachment will fall into the collecting bin and damage the delivery means when the plant is started. Also, it is very dirty in the compartment containing the bags and thus a very undesirable place in which to work.